Molecularly-thin cellulose nanoribbons (CR) as superior reinforcing agents for PVA composites: A comparative study...

Polyvinyl alcohol (PVA) films are promising for biodegradable packaging; however, their use is limited by low mechanical strength. This study introduces a novel cellulose nanoribbon (CR) with molecular-scale thickness as a high-performance filler to overcome the reinforcement-toughening trade-off in cellulose nanomaterials. CR was exfoliated from softwood pulp using hydrogen peroxide/acetic acid-assisted ultrasonication. The reinforcement mechanisms of CR, cellulose nanofibrils (CNF), and cellulose nanocrystals (CNC) in PVA matrices were examined and compared. Structural analysis showed CR's ultrathin, ribbon-like shape (∼0.8 nm thick). Mechanical tests showed CR enhances tensile strength and maintains ductility: at 10 wt%, the tensile strength and Young's modulus of PVA/CR reached 62.7 MPa and 2.92 GPa, which is 184% and 225% increases over pure PVA, while retaining an elongation at break of 121%, a value significantly higher than that of PVA/CNF (73%) and PVA/CNC (68%). This is due to the uniform dispersion of CR and their formation of dense hydrogen bonds with PVA, improving stress transfer and toughness. The composites also retain optical transparency and thermal stability. Results show molecular CR as an effective, sustainable reinforcement capable of overcoming the strength-toughness trade-off, offering a new design for high-performance, eco-friendly composites.